An installation can change its scheduling characteristics using different versions of the ASCHPMxx parmlib member. For example, one parmlib member might contain setup values, while others contain statements that add new classes of transaction initiators (CLASSADD) or delete previous classes (CLASSDEL). The parmlib member may also re-specify statements with new parameter values to modify previous statements.

Attention: When modifying previous statements by respecifying them, the parmlib statements have a cumulative effect, and any one parmlib member might not contain the current scheduling information. If you use the CANCEL command to terminate the ASCH address space, you must respecify each parmlib member in its former order to reconstruct the previous scheduling definitions.

When parmlib statements are initially specified, omitted optional parameters receive default values. When parmlib statements are re-specified, however, omitted parameters in the CLASSADD statement assume the defaults, but omitted parameters in the OPTIONS and TPDEFAULT statements do not assume the defaults.

For example, a class is defined with specific characteristics by a CLASSADD statement. When another CLASSADD statement identifies the same class name but omits the MAX and MIN parameters, MAX assumes the default of 1 and MIN assumes the default of 0.

Therefore, to guarantee that intended values are not overridden by default values, re-specify all keywords on modifying statements.